WO2012172237A1

WO2012172237A1 - Method and device for controlling a electric motor propulsion unit with decoupled controls

Info

Publication number: WO2012172237A1
Application number: PCT/FR2012/051277
Authority: WO
Inventors: Abdelmalek Maloum; Ahmed Ketfi-Cherif
Original assignee: Renault S.A.S.
Priority date: 2011-06-15
Filing date: 2012-06-07
Publication date: 2012-12-20
Also published as: FR2976746A1; CN103688461A; JP2014517677A; EP2721729A1; US20140132196A1; FR2976746B1; EP2721729B1; JP6041870B2; US9608553B2

Abstract

Method of controlling an electric motor furnished with a rotor and a stator, sensors for measuring currents flowing in the rotor and in the stator, means for determining setpoints of current and means for processing the signals from the measurement sensors, characterized by the fact that it comprises steps in the course of which: intermediate signals are determined by a transformation according to which stator voltages and rotor voltages of the electric motor are expressed in a decoupled reference system as a function of the signals received from the processing means, and signals for regulating voltage as a function of the currents flowing in the rotor and in the stator of the electric motor satisfying the setpoints of current are determined as a function of the intermediate signals obtained by transformation.

Description

METHOD AND DEVICE FOR CONTROLLING AN ELECTRIC MOTOR POWERTRAIN WITH S

The technical field of the invention is the control of electric motors, and in particular the field of electric motors of the synchronous type with wound rotor.

A synchronous synchronous motor with wound rotor comprises a fixed part called stator and a mobile part called rotor. The stator comprises three coils offset by 120 ° and supplied with alternating current. The rotor comprises a coil supplied with direct current.

The currents of the stator phases depend on the resistances and inductances of the rotor and the stator as well as on the mutual inductance between the rotor and the stator.

An object of the present invention is to improve the control quality of the currents of a synchronous synchronous motor with a wound rotor, which can be reached by a regulator of the state of the art.

According to one embodiment, a method of controlling a system comprising an electric motor equipped with a rotor and a stator, sensors for measuring the currents flowing in the rotor and in the stator, means method for determining current setpoints and signal processing means from the measurement sensors, characterized in that it comprises steps in which:

intermediate signals are determined by a transformation according to which stator and rotor voltages of the electric motor are expressed in a decoupled reference frame as a function of the signals received from the processing means, and

according to the intermediate signals obtained by transforming, voltage regulation signals are determined as a function of the circulating currents in the rotor and in the stator of the electric motor satisfying the current instructions. These translate a torque instruction.

The control method has the advantage of a complete decoupling between the rotor current variations and the stator current variations allowing torque setpoint tracking to be improved. This decoupling is much less complex than the decoupling performed in conventional coupling compensation devices working in the Park marker.

The control method may comprise a step in which the regulation voltage signals are saturated to satisfy the constraints associated with a battery fitted to a motor vehicle and connected to the electric motor.

The control method may comprise a step in which integration limits are determined by applying an inverse transformation to said saturated voltage control signals, the integration limits applying to the determination of new intermediate signals after said inverse transformation.

The control method may comprise a step in which the continuity of the controls is ensured by limiting the variations of the commands actually transmitted to the actuators.

According to another embodiment, a control system of an electric motor equipped with a rotor and a stator, comprising sensors for measuring circulating currents in the rotor and in the stator, and means for determination of current instructions, characterized in that it comprises:

means for processing the measurements and queries connected at input to the measurement sensors and to the means for determining current setpoints,

transformation means providing intermediate signals after a transformation according to which stator and rotor voltages of the electric motor are expressed in a decoupled reference frame, input connected to the processing means of the measurements and requests,

determining means connected at input to the transforming means, the determining means being adapted to transmit voltage regulation signals of the electric motor satisfying the current instructions.

The control system may include a saturator of voltage regulation signals received from the determining means.

The control system may comprise means for inverse transformation of the saturated voltage regulation signals received from the saturator. The control system may include means for processing the outputs of the saturated voltage regulation signals received from the saturator.

Other objects, features and advantages will become apparent upon reading the following description given solely as a non-limitative example and with reference to the accompanying drawings, in which:

FIG. 1 illustrates a control method of an electric powertrain, and

FIG. 2 illustrates a device for controlling an electric powertrain.

The regulation of the currents of a synchronous motor with wound rotor presents difficulties because of the synchronization of the sinusoidal currents of the stator with the rotation of the motor and the dynamic coupling between the rotor and the stator.

For this, we have an inverter to control the voltage of the stator phases and a chopper to control the rotor voltage.

Rather than using sinusoidal setpoints, the Park transform is used to regulate constant signals. The stator control signals in the Park marker are noted

V _d , V. The regulation signal of the rotor is noted V _f .

In known manner, there are the following equalities:

dl, dl _ç

V, = RI, + L, - + M _~ - - LI (Eq I)

dsdd dt f dt rqq ⁷ (Eq II)

d ^I f dld

V "= Pv, I, + L _f ^ + aM _f - (Eq III)

ff f dtf dt

In equations (I) and (III), we note that:

- Vd depends on the current variation Ι ^, the current variation 1 ^, (dynamic coupling), and currents 1 ^ and I -Vf depends on the current variation, the current variation 1 ^ (dynamic coupling) and the current 1 ^,.

The dependence of Vd and Vf on these current variations (dynamic coupling) is troublesome from a control point of view because a variation of Vd or Vf will cause a variation on the current I. and on the current Ι ^,, which makes their control coupled.

In order to overcome this dynamic coupling between the current variation I. and the variation of current I, , we make a d f

change of variables, to express the stator and rotor voltages in a decoupled frame, that is to say in which the variation of the current I. only depends on a single voltage Y-, with i an index equal to d, q or f and j an index equal to x, y or z.

After this change of variables: (V _x , V _y , V _z ) = f (V _d , V, V _f ), the system to be controlled can then be represented by the following equations:

With:

V _x : New stator voltage in the decoupled reference frame of the axis d.

V _y : New stator voltage in the decoupled reference frame of the q axis.

V _z : New rotor voltage in the reference frame decoupled from the axis f.

Equivalent inductance of armature on the axis d, that is to say on the polar axis of the Park mark. L _q : Equivalent armature inductance on the q axis, that is to say on the interpolar or transverse axis of the Park mark.

L _f : Rotor inductance.

R _s : Equivalent resistance of stator windings.

R _f : Resistance of the rotor.

M _f : Mutual inductance between the stator and the rotor.

Id: Stator current on the axis d, that is to say on the polar axis of the Park marker.

I _q : Stator current on the axis q, that is to say on the interpolar or transverse axis of the Park mark.

I _f : Rotor current.

co _r : Speed of rotation.

The values La, L _q , L _f , R _s , R _f and M _f are known from prior measurements.

The main difficulties presented by this type of system reside in the dynamic coupling between the axes d and f, the hardly identifiable variation of the parameters, and finally the voltage constraints of the supply battery.

The voltage constraints are as follows:

V, ² + V ² ≤ 3 ^ q.

o <v _f ≤ v _bat

With Vbat: the voltage of the battery The control method illustrated in FIG. 1 makes it possible to control the currents la, I _q and I _f to satisfy the demands in torque at the wheel. For this purpose, filtered and scaled measurements as well as reference current references (which translate the setpoint torque) that the controller must achieve are available.

In a first step 1, in the decoupled frame of reference, the synthesis of the regulator is carried out which is of the following form:

v _x = K _d (l -I _d ) + K _id j (l -I _d )

V _y = K _q (lf -I _q ) ₊ Kj (lf -I _q ) (Eq.3) v _z = K _f (l -I _f ) + K _if } (l -I _f )

With I _d : the reference stator current on the axis d.

I ^r : the reference stator current on the q axis.

If ^r : the current of the reference rotor

K _d , K _q , K _f , K _id , K _iq , K _if : setting parameters.

The synthesis of the regulator is thus carried out in the decoupled frame of reference and not in the frame of reference of Park.

The currents V, l _q ^r and I _f ^ref are setpoint currents from the processing means 6. The equality (Eq. 1) = (Eq.3) makes it possible to determine the adjustment parameters K _d , K _q , K _f , K _id , K _iq , K _if .

As can be seen, the regulator makes it possible to determine a voltage along an axis x (V _x ) depending only on the current variations of the axis d (la). Similarly, the voltage along an axis y (V) and the voltage along an axis z (V _z ) respectively depend only on the current variations of the axis q (I _q ) and the rotor (If). Couplings are minimized at the controller.

The voltage signals expressed in this new base (V _x , V _y , V _z ) are intermediate signals. In order to have access to real values, an inverse transformation is necessary. For this purpose, during a second step 2, the voltage regulation signals actually applied to the system are calculated:

The voltage regulation signals Vd, Vq, Vf are thus determined as a function of the intermediate signals, the values of the physical parameters of the motor (inductances, resistors, etc.) and the currents flowing in the motor (la, I _q , If ).

In a third step 3, the voltage regulation signals calculated in the second step are saturated to satisfy the constraints related to the battery (by satisfying the equation 2).

In a fourth step 4, integration limits are determined by inverting the saturated regulation signals calculated in the third step by applying an inverted matrix with respect to the matrix of equation 4. The integration limits are thus expressed in the formalism of the decoupled referential V _x , V, V _Z. The Integration limits are then taken into account in step 1 in order to limit the integrations of the second terms of equation 3. The integrations are stopped when the values V _x , V _y , V _z exceed the saturated values of V _x , V, V _Z obtained in step

4.

A fifth step 5 ensures the continuity of orders by limiting the variations thereof. After step 5, the values of sinusoidal U, V, W simple voltages are calculated (inverse Park transform) and serve as voltages to be applied to the real system.

The control method obtained is efficient from a point of view of reliability and robust against disturbances.

FIG. 2 shows a control device comprising means for processing measurements and queries, capable of filtering and scaling signals received from sensors, for example current sensors Ia, _Iq and I _f .

The processing means 6 is connected at the output to the transformation means 7 making it possible to determine the signals V _x , V _y , V _z , that is to say the intermediate signals. The transformation means 7 applies equation 3 and equation 1.

The transformation means 7 is connected at the output to a determining means 8 able to determine the voltage regulation signals Vd, V _q , V _f as a function of the intermediate signals V _x , V _y , V _z . The determining means 8 applies equation 4.

The determination means 8 is connected at the output to a saturator 9 which is able to limit the voltage regulation signals V _d , V _q , V _f according to the equation 2.

The saturator 9 is connected at the output to an inverting means 10 and a means for processing the outlets 11.

The inverting means 10 is capable of determining saturated intermediate signals as a function of the saturated voltage regulation signals received from the saturator 9. For this, the inverting means 10 applies an inverse matrix of the matrix of equation 4 The saturated intermediate signals are then transmitted to the transformation means 7.

The output processing means 11 is able to limit the variation of the saturated voltage regulation signals transmitted to the actuators between two cycles of calculation so that the mechanical stresses and operating jolts are limited.

Claims

1. A method of controlling a system comprising an electric motor having a rotor and a stator, sensors for measuring circulating currents in the rotor and in the stator, means for determining current instructions and processing means (6) signals from the measurement sensors, characterized in that it comprises steps in which:

intermediate signals are determined by a transformation according to which stator and rotor voltages of the electric motor are expressed in a decoupled reference frame as a function of the signals received from the processing means (6), and

according to the intermediate signals obtained by transforming, voltage regulation signals are determined as a function of the circulating currents in the rotor and in the stator of the electric motor satisfying the current instructions.

2. Control method according to claim 1, comprising a step in which the voltage regulation signals are saturated to meet the constraints of a battery fitted to a motor vehicle and connected to the electric motor.

3. A control method according to claim 2, comprising a step in which integration limits are determined by applying an inverse transformation to said saturated voltage control signals, the integration limits applying to the determination of new signals. intermediate after said inverse transformation.

4. Control method according to claim 3, comprising a step in which it ensures the continuity of orders by limiting the variations of these commands.

5. Control system of an electric motor having a rotor and a stator, comprising sensors for measuring circulating currents in the rotor and in the stator and means for determining current setpoints, characterized in that that it includes:

means for processing (6) the measurements and queries connected at input to the measurement sensors and to the means for determining current setpoints, transformation means (7) providing intermediate signals after a transformation according to which stator and rotor voltages of the electric motor are expressed in a decoupled reference frame, input connected to the processing means (6) of measurements and requests,

determination means (8) connected at input to the transformation means (7), the determining means (8) being adapted to transmit voltage regulation signals of the electric motor satisfying the current instructions.

6. Control system according to claim 5, comprising a saturator (9) voltage regulation signals received from the determining means (8).

7. Control system according to claim 6, comprising means for inverse transformation (10) saturated voltage regulation signals received from the saturator (9).

8. Control system according to claim 7, comprising a means (1 1) for processing the outputs of the saturated voltage regulation signals received from the saturator (9).